MMI DOOR Exterior Prehung Door User Manual

How to Measure for an Exterior Prehung Door
A pre-hung door is a door that is already hanging in its own frame. It’s an all-in-one package that ensures the smoothest possible installation of your door. We recommend a prehung door if your situation is one of the following:
- No existing door frame
- The existing door frame is damaged
- New Construction
Note:
When installing an exterior door, unless you are a pro, it’s extremely hard to tight-fit an exterior slab door.
- Prehung doors come with weather-stripping and are tight-fitting off the shelf.
- A tight-fit door will save you on your energy bill.
What to consider when buying a pre-hung door?
- Make sure the new door frame will fit the rough opening. We recommend a rough opening that is slightly larger than the outside unit dimension of the new prehung door. This allows for shimming to level the unit.
- Jamb width refers to the thickness of the wall. The jamb needs to cover the stud plus any wall application such as drywall or sidings.
- Know your door handling (swing). Stand with your back against the hinge side of the frame and extend an arm in the direction you wish the door to open. If you extended the left arm, then you need to order a LEFT-HANDED door. If you extended the right arm, then you need to order a RIGHT-HANDED door.
- Though exterior doors typically swing inward, outswing exterior doors are available. So be sure to add “inswing” or “outswing” to your notes before ordering.

Door size. Measure the width and height of your old door. Round these up to full inches to find the size of the replacement door you’ll need. If, for example, your door measures 35-3/4 in. wide and 79-1/2 in. tall, you’ll order a 36 in. by 80 in. door. For double doors this will be the total of both doors. For example, two 36 in. by 80 in. doors equal one 60 in. by 80 in. door size. Similarly, for a single door with sidelite(s), the width of the sidelite(s) will need to be added to the door width.
- Jamb (Frame) width. Measure from the backside of the interior trim to the backside of the exterior trim (Figure A). Specify this jamb width when you order your new prehung door. This guarantees that the interior trim will fit flush to the wall without adding “jamb extensions.”

- Rough opening. You’ll have to remove the interior trim to get accurate measurements of the rough opening. Measure the opening width between framing members and from the bottom of the sill to the top of the opening. Compare these measurements to the rough opening requirements of your new door to make sure it will fit.
How to accurately measure the rough opening
- Measure the widths between the studs of the entryway 3 times; from the highest points of the opening, the center points, and the lowest points. Record the smallest width of the 3 measurements.
- Measure the height (from the bottom of the sill to the top of the opening) on both sides and record the smallest measurement of the 2.
Rough opening recommendations
Getting the rough opening size right the first time will save you from frustration when installing your doors. Framing and calculating rough opening sizes is quite simple.
Tip:
Not all rough openings are completely plumb and square. Leaving extra space allows you to perfectly plumb, level and square your door installation.
Single Door
Frame (Unit) Dimension:
Width: Add 1-1/2 in. to the width of the actual door Height: Add 1-3/4 in. to the height of the actual door
- For outswing unit height, add 1 in. to the height of the actual door
- Rough Opening: Width: Add 2-1/2″ to the width of the actual door
- Height: Add 2-1/4″ to the height of the actual door
- For outswing rough opening height, add 1-1/2 in. to the height of the actual door
Double Doors
- Frame (Unit) Dimension:
- Width: Add 2″ to the width of the actual two doors
- Height: Add 1-3/4″ to the height of the actual doors
- Rough Opening:
- Width: Add 3″ to the width of the actual two doors
- Height: Add 2-1/4″ to the height of the actual doors
- Door and one sideline
- Frame (Unit) Dimension:
- Width: Add 2-1/4″ to the width of the actual door and sidelight Height: Add 1-3/4″ to the height of the actual door
- Rough Opening:
- Width: Add 3-1/4″ to the width of the actual door and sidelight Height: Add 2-1/4″ to the height of the actual door
- Door and two sidelites
- Frame (Unit) Dimension:
- Width: Add 3″ to the width of the actual door and two side lites Height: Add 1-3/4″ to the height of the actual door
- Rough Opening:
- Width: Add 4″ to the width of the actual door and two side lites Height: Add 2-1/4″ to the height of the actual door
MMI DOOR Exterior Prehung Door User Manual



















